James Crumbley, the father of Michigan school shooter Ethan Crumbley, vowed to “go on a rampage” against the prosecutor in his case following his at least 10-year prison stint, according to jailhouse phone calls. Earlier this week, James and his wife Jenner Crumbley were both sentenced to 10-15 years behind bars after they were convicted of involuntary manslaughter for the 2021 Oxford High School shooting perpetrated by their then-15-year-old son, Ethan Crumbley, HNGN previously reported. They were the first parents to be convicted in a U.S. mass school shooting in the case prosecuted by Oakla…